1) Field of the Invention
The present invention relates to an optical switch apparatus and a control information updating method therein, which are suitable for use in the construction of an optical communication system in which a large capacity of information modulated into an optical signal is handleable as an optical signal without being converted into an electric signal, and more particularly to an optical switch apparatus and a control information updating method therein suitable for use in a network which is made to conduct optical burst signal processing.
2) Description of the Related Art
In the case of a photonic network in a metro access area, a network configuration is frequently changed through the exchange/route-switching of a line or signal at ADM (Add Drop Multiplexing). At a repeating stage or the like in the current network, in large quantities there have been employed configurations which are designed to carry out the signal switching by once converting an optical signal into an electric signal and then making the conversion into an optical signal.
However, in the future, it is expectable that they are replaced with a dynamic OADM (Optical Add Drop Multiplexing) system made to separate only a desired wavelength in a state of an optical signal or an optical cross connect node or the like made to carry out the switching of an input/output route in units of wavelength in a state of an optical signal. Moreover, in the next generation, for the enhancement of line utilization efficiency, there will be a need to have a function to carry out processing (in this specification, these processing will be referred to generally as optical burst signal processing) in which an optical signal is divided into frames each having a fixed length so that the exchange/route-switching is made in units of frame in a state of the optical signal.
In such an optical burst signal processing handling transmission apparatus, it is expected to, for conducting the exchange or route-switching in units of the aforesaid frame, carry out the switching processing in a time dimension shorter than at least millisecond dimension.
A patent document 1 (Japanese Patent Laid-Open No. 2002-318398) discloses a technique related to an optical switch module using an optical deflecting element. For example, as shown in FIG. 15, there is described an optical switch module 100 comprising an input side (incidence side) optical waveguide unit 101, a collimating unit 102, an input side optical deflecting element unit 103, a common optical waveguide 104, an output side (outgoing side) optical deflecting element unit 105, an optical collecting unit 106 and an output side optical waveguide unit 107.
Each of the input side and output side optical waveguide units 101 and 107 has a plurality of optical waveguides 101a (#11 to #1n) or a plurality of optical waveguides 107a (#21 to #2n), and each of the input side and output side optical deflecting element units 103 and 105 has n optical deflecting elements 103a or 105a. Moreover, the optical deflecting element 103a or 105a is made to conduct the route switching with respect to a signal light inputted through the optical waveguide 101a for outputting it through a desired optical waveguide 107a. 
As the other well-known techniques, there are techniques disclosed in Japanese Patent Laid-Open Nos. 2003-185984 (patent document 2), 2000-114629 (patent document 3), 2000-269892 (patent document 4), HEI 7-212315 (patent document 5) and HEI 10-228007 (patent document 6).
As mentioned above, in a case in which consideration is given to the switching processing in units of frame in a time dimension shorter than millisecond dimension, there is a need to successively carry out the route switching with respect to frame signal lights inputted through various paths. At this time, different output power values appear among frame signal lights to be outputted due to difference in input power, difference in loss between optical switch ports, or the like, which affects the error-free reception in an optical receiver.
The technique disclosed in the above-mentioned patent document 1 is remote from a configuration which can eliminate the difference in output power value among the frame signal lights.
As FIG. 16 shows, the patent document 2 discloses a technique in which, for varying the intensity of light inputted from an optical transmission line 211, an optical deflector 215 for making a different optical axis of an outputted light with respect to an optical axis of an optical transmission line 212 is disposed through lenses 213 and 214 between the optical transmission lines 211 and 212. However, a concrete control mode of varying the intensity of an inputted light is not disclosed by this optical deflector.
Although the patent documents 3 to 6 disclose a variable optical attenuator for feedbacking an attenuation quantity (value) of an outputted light for carrying out variable control, through such feedback control, difficulty is experienced in executing the control to make the output power value constant with respect to a frame signal light undergoing the switching processing in a time dimension shorter than a millisecond dimension. This is because the signal light passes at the time that the feedback control works.
In addition to the case of conducting the aforesaid optical burst signal processing, also in the case of common optical signal transmission, when difficulty is encountered in eliminating the fluctuation of optical power with a response in a time dimension (for example, microsecond dimension) shorter than milliseconds, it can interfere with the error-free reception as well as the above-mentioned case.
Moreover, in the technique disclosed in the aforesaid patent document 1, in a case in which, as shown in FIG. 15, with respect to a signal light from the input side optical waveguide 101a (#11 to #1n), the output route is switched to one of the n output side optical waveguide 107a (#21 to #2n), there is a need to apply a voltage corresponding to a deflection angle to each of the input side and output side optical deflecting elements 103a and 105a. Moreover, the deflection angles needed for the route switching functions in the input side and output side optical deflecting elements 103a and 105a vary in accordance with the disposition positions.
For example, in the optical deflecting element 103a for deflecting the light from the optical waveguide 101a (#11), there is a need to vary the light in a range from the angle of the straight-advancing direction of leading to the optical waveguide 107a (#21n) in the illustration to the right-side deflection angle of leading to the optical waveguide 107a (#2n) therein, while in the optical deflecting element 103a for deflecting the light from the optical waveguide 101a (#13), there is a need to vary the light in a range from the left-side deflection angle of leading to the optical waveguide 107a (#21) in the illustration to the right-side deflection angle of leading to the optical waveguide 107a (#2n) therein. This also applies to the output side optical deflecting elements 105a. 
Therefore, there is a problem which arises with the route switching in that the maximum voltage to be supplied to each of the optical deflecting elements 103a and 105a varies in accordance with the disposition position, which complicates the voltage setting and the circuit arrangement for the supply of a voltage to the optical deflecting element 103a, 105a. 